Estimates Of Sediment Production Research Articles

Evaluation of reservoir sedimentation using bathymetry survey: a case study on Adebra night storage reservoir, Ethiopia

Reservoir sedimentation is a serious challenge that reduces reservoir life. Because it decreases the initial capacity of the reservoir and has an impact on drinking water supply, irrigation, and hydropower activities. Inadequate land activities and poor management techniques cause soil erosion and reduce reservoir storage capacity. As a result, accurate sediment estimation was assist in the adoption of sustainable land-use activities and best management practices that lead to effective reservoir operations. The main objective of this study was to evaluate the rate of sedimentation and remaining capacity of Adebra night storage reservoir (NSR) using a bathymetric survey and Arc-GIS 10.8. A comparison of original and current reservoir capacity was used to evaluate the quantity of sediment deposition in the reservoir. The latter was developed using Arc-GIS 10.8 and a bathymetry survey that was used to develop the TIN surface and evaluate reservoir volume. The Adebra NSR reservoir capacity was decreased by the accumulation of sedimentation from 36,902 m3 in 2012 to 27,722 m3 in 2020. The results of this study showed that the Adebra night storage reservoir had lost on average 24.8% of its capacity due to sedimentation, during 8 years of operation. The average deposition rate of sedimentation in Adebra NSR was estimated to be 1147.5 m3/year, with a loss rate of 3.1% per year. The value of sedimentation rates found in live storage of the reservoir area was 1147.5 m3/year. At the current time, the expected life of the night storage reservoir was reduced due to a lack of proper soil conservation practices in the reservoir catchment areas. In general, the study finding showed that the capacity of NSR was reduced by the accumulation of sedimentation year to year throughout the design period. Therefore, to improve the capacity of NSR should be planning and implementing different techniques of sediment control and removal, depending on the estimation of sediment production from watersheds of inlets and outlets of reservoirs.

Estimation of sediment production and soil loss in a water supply basin for the metropolitan region of São Paulo - Brazil

The Jaguarí river basin has outstanding importance in the national scenario for being located between the largest industrial and population centers in the country and for the process that involves the management of its water resources. The main purpose of the basin's reservoirs is to supply water to the population of the metropolitan region of São Paulo, and before that, there are pressures and conflicts between the different actors interested in water resources, as well as creating protection policies, establishing the need for sustainable use conservation units, support environmental protection policies, resulting in proposals for nature conservation measures and promotion of the population's quality of life. Hydrological models represent an alternative to verify the impacts resulting from anthropic actions in water availability and production of sediments in large hydrographic basins. The models can simulate/indicate how changes in the environment are reflected in the hydro sedimentological balance of a basin. This study aims to assess soil loss in the Jaguari River basin using the Soil and Water Assessment Tool (SWAT) to determine quantity and quality of the sediment production, the loss of soil, and resulting impacts to the Jaguarí River basin. Calibration and validation were performed to verify the suitability of the model and the spatialization of the factors that make up the Modified Universal Soil Loss Equation (MUSLE). The SWAT model proved to be suitable for the simulation of sediments; although the basin does not present a large area with potential for erosion risk, conservation measures can be taken to effectively control soil loss in susceptible areas. The average soil loss in the basin was 1.71 Mg ha−1 year−1 and the simulated and observed Sediment Delivery Rate (SDR) was 5.5% and 4.7%, respectively.

Estimation of sediment production in oil palm expansion areas in the Amazon

ABSTRACT Currently, an activity that has become strategic at a national level is the cultivation of oil palm (Elaeis guineensis) in the northeast region of the Pará State, in eastern Brazilian Amazon. However, the impacts of this crop expansion on the hydro-sedimentological cycle are still unknown. Therefore, this study estimated the impacts of oil palm crop expansion on sediment production in a sub-basin under consolidated use of this crop. The Soil and Water Assessment Tool (SWAT) model was applied in the Mariquita sub-basin, calibrated by the flow regionalization technique, using data measured in the field with a current meter. Simulation results indicated an increase in sediment production between the years 2008 and 2013, which can be attributed to the large reduction of areas of secondary vegetation that were replaced by pasture, oil palm and general agriculture. Oil palm areas had a lower average monthly sediment yield in the rainiest period in all simulated years, compared with areas of general agriculture and pasture.

Estimation of sediment production from weathered bedrock in different lithology due to freeze-thaw action

Estimation of sediment production from weathered bedrock in different lithology due to freeze-thaw action

Comparison of measured 137Cs data and USLE/ RUSLE simulated long-term erosion rates

The 137Cs technique of quantifying soil erosion is used to provide field data to compare with the empirical model USLE/RUSLE for predicting long-term erosion rates in afforested lands. Caesium-137 from atmospheric nuclear-weapons tests in the 1950s and 1960s, deposited worldwide on the land surface by precipitation, has become an important tool for assessing soil erosion and sedimentation in a wide variety of environments. The underlying hypothesis to support the use of 137Cs measurements to estimate rates of erosion or sedimentation is the assumption that a reliable relationship can be established between the degree of increase or depletion of the soil caesium-137 inventory relative to the baseline or reference inventory and the total depth of soil loss or accumulation. The reference inventory is usually established by sampling adjacent, stable sites, where neither erosion nor deposition has occurred. Where sample inventories are lower than the local reference inventory, erosion may be inferred. Similarly, sample inventories beyond the reference level are indicative of deposition. Estimation of sediment production by erosion has traditionally been solved through the use of empirical models as USLE and its corrected version RUSLE (Renard et al., 1997), and extensive work has been done regarding calibration and validation of its main parameters under Uruguayan local conditions (Clérici y García Prèchac, 2001). The results of a trial run of the technique on Eucalyptus forested microcatchment (97 ha) are presented. The expected distribution of deposition was derived from the reference sample activity: 373,5 Bq/m2. Evidence of soil erosion in the catchment’s middle slope was deduced whereas soil cores from the lower slope had more than expected activity indicating deposition. Results indicate a good agreement between the 137Cs data and USLE/ RUSLE predicted erosion in the slope.

Comparison of measured 137Cs data and USLE/ RUSLE simulated long-term erosion rates

The 137Cs technique of quantifying soil erosion is used to provide field data to compare with the empirical model USLE/RUSLE for predicting long-term erosion rates in afforested lands. Caesium-137 from atmospheric nuclear-weapons tests in the 1950s and 1960s, deposited worldwide on the land surface by precipitation, has become an important tool for assessing soil erosion and sedimentation in a wide variety of environments. The underlying hypothesis to support the use of 137Cs measurements to estimate rates of erosion or sedimentation is the assumption that a reliable relationship can be established between the degree of increase or depletion of the soil caesium-137 inventory relative to the baseline or reference inventory and the total depth of soil loss or accumulation. The reference inventory is usually established by sampling adjacent, stable sites, where neither erosion nor deposition has occurred. Where sample inventories are lower than the local reference inventory, erosion may be inferred. Similarly, sample inventories beyond the reference level are indicative of deposition. Estimation of sediment production by erosion has traditionally been solved through the use of empirical models as USLE and its corrected version RUSLE (Renard et al., 1997), and extensive work has been done regarding calibration and validation of its main parameters under Uruguayan local conditions (Clerici y Garcia Prechac, 2001). The results of a trial run of the technique on Eucalyptus forested microcatchment (97 ha) are presented. The expected distribution of deposition was derived from the reference sample activity: 373,5 Bq/m2. Evidence of soil erosion in the catchment’s middle slope was deduced whereas soil cores from the lower slope had more than expected activity indicating deposition. Results indicate a good agreement between the 137Cs data and USLE/ RUSLE predicted erosion in the slope.

Holocene Sediment Production in Lillooet River Basin, British Colombia: A Sediment Budget Approach

A sediment budget approach is used to investigate the sources, storage, and yield of clastic sediment in Lillooet River watershed, in the southern Coast Mountains. The 3150 km2 basin is heavily glacierised, and includes a Quaternary volcanic complex which has been active in the Holocene. The sediment yield has been determined from the rate of advance of the delta at the basin outlet. The floodplain of the main river valley is aggrading as the delta advances, and probably has been through most of the Holocene. Major sediment sources in the basin include glaciers and Neoglacial deposits, debris flows, and landslides in the Quaternary volcanic complex. Soil and bedrock creep, bank erosion of Pleistocene glacial deposits, and sediment from logging and agriculture are probably of minor importance. Estimates of sediment production from these sources explain only about half the observed clastic sediment yield plus the rate of valley aggradation. The unexplained sediment production may be associated with paraglacial sediments exposed by glacial retreat from the nineteenth century Neoglacial maximum; alternatively the frequency of occurrence of intermediate scale debris flows and landslides has been seriously underestimated. Sediment supply is highly episodic over time scales of centuries to thousands of years. Major factors in the temporal pattern of Holocene sediment supply are periods of volcanism, large landslides, the retreat of glaciers from the Neoglacial maximum, and recent river engineering works.

Gully erosion in the Siwalik Hills, Nepal: estimation of sediment production from active ephemeral gullies

AbstractA simple field‐based monitoring programme was established in a small catchment (area 4·6 km2) to find the rates of gully erosion in the Siwalik Hills, Nepal. The rates are used to estimate the amount of sediment produced by gully erosion in the catchment. Three large and active gullies were selected with areas ranging from 0·44 to 0·78 ha. Aerial photographs taken in 1964, 1978 and 1992 were ortho‐rectified and used to study the dynamics of gully heads. The same gullies were also monitored manually using an orthogonal reference system fixed by erosion pins around the gully heads. Results from the aerial photos indicated that the gullies expanded remarkably over the period from 1964 to 1992, by 34 to 58 per cent. Head‐retreat rates during that period were 0·48, 0·55 and 0·73 m a−1 and average annual sediment evacuation was estimated as 2534 ± 171, 959 ± 60 and 2783 ± 118 m3 a−1 for the three gullies respectively. From the field measurement, estimated volumes were found to vary from 731 ± 57 to 2793 ± 201 m3 a−1 over the monitoring period of two years. It was also found that the gullies produce sediment which accounts for up to 59 per cent of the sediment produced from surface erosion in the headwater catchment. The findings are useful for planning and executing appropriate control measures and constructing a sediment hazard map at the catchment scale. Copyright © 2006 John Wiley & Sons, Ltd.

Gully erosion and sediment production: Te Weraroa Stream, New Zealand

We derive a sediment budget for Te Weraroa Stream, New Zealand, the principal drainage in a small (29 km2) steepland catchment where gully erosion, triggered by conversion to pasture early in the twentieth century, was ameliorated by reforestation that commenced in 1962. Estimates of sediment production were made using the change in gully area observed in sequential aerial photographs. Channel storage was assessed from stream cross‐section surveys. At its peak, gully erosion affected ∼6% of the total catchment area. The amount of sediment contributed from gullies declined by 62% as the forest became established, but of the 28.7 Mt of sediment generated by gully erosion between 1950 and 1988, 48% was stored in the channel along the lower 8 km of Te Weraroa Stream. Even if the amount of sediment generated by gully erosion continues to decline, it likely will be many decades before the gravel is released from storage.

Global Oil Productivity Evaluated from the Comparison between Sediment Production and Mantle Fluxes

Hydrocarbons in sedimentary basins can, on a global scale, be considered as that part of the sedimentary production which escaped subduction. That escape must either correspond to passive margins or occur in the early stages of the subduction process because, as shown by experimental studies, once carbon has entered the field of high pressure subduction metamorphism it remains stable throughout down to upper mantle conditions, either as primary carbonate or graphite or as secondary carbonate derived from oxydation of the reduced carbon. Hence, if sedimentary production and mantle fluxes are reasonably constrained, the global oil and gas productivity can be determined as the difference between sedimentary production and subduction flux. Unlike some other elements (notably nitrogen) carbon appears to be in a steady state situation for surface mantle exchanges, as reflected by the very uniform isotopic composition of mantle carbon (exotic values correspond to less than 1% of the samples), with an average value at ~13C -4%0 (Javoy and Pineau, 1991) Carbon fluxes in both directions, deduced from ridge outgassing are of the order of 1 -2 1014g Carbon /year. This is significantly less than the estimates of sediment production. The simplest way to explain the difference is through the escape of mobile carbon-bearing phases, both oxidized (CO2) and reduced (hydrocarbons). In order to constrain these fluxes one has to know the proportion of reduced and oxidized carbon both in the sedimentary production and in subduction flux. The later is readily obtained through the 813C of the total subduction flux (-4%0), which corresponds to15% reduced carbon, the total flux being also well constrained at 1.8 10lag/year. There is more uncertainty on the sedimentary production. After organic matter diagenesis the fluxes are estimated to between 2 and 2.8 10lag/year, (which would correspond to a subduction efficiency of between 60 and 90% ) and a reduced carbon/oxidized carbon ratio between 1:3 and 1:4 according to the relative importance given to shales vs carbonates and their reduced carbon content.With these numbers one obtains oil and gas (including COE) productivities between 70 and 40%, with fluxes between 66 and 17 million tons/year. Of course the input data, and especially the sedimentary production, have to be refined, but this shows that one can arrive at the evaluation of global resources' productivity. It is also possible to calculate the CO2 flux generated together with the hydrocarbon flux.